Waveguide crystal assembly for broadband operations



y 1960 J- H. VOGELMAN 2,939,005

WAVEGUIDE CRYSTAL ASSEMBLY FOR BROADBAND OPERATIONS Filed Oct. 18, 1956 S 26 12/ V l Irma/. 5

iiniteri States Patent WAVEGUIDE CRYSTAL ASSEMBLY FOR BROADBAND OPERATIONS Joseph H. Vogelman, Rome, N.Y., assignor to the United States of America as represented by the Secretary of the Air Force Filed Oct. 18, 1956, Ser. No. 616,899 3 Claims. (Cl. 250-31) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a microwave waveguide structure incorporating a crystal suitable for use as a detector and/or mixer for extremely broadband use with good R.F. characteristics.

Present microwave crystal mixer and detector units are designed for use in a linear or coaxial shaped waveguide which results in difficult microwave configurations and inherently narrow bandwidth characteristics.

Previous utilization of a crystal in waveguide application involved physical incorporation of the crystal in the waveguide so that the natural configuration would result in a minimum discontinuity; however, this type of crystal design is inadequate in that it will only encompass a narrow frequency band due to the cut-off limitations on the waveguide structure which makes up the crystal unit and it also limits the external circuitry because of the large change in the ratio of waveguide wavelength to free space wavelength which is encountered when attempting to use the crystal over a broad band.

Accordingly, it is an object of this invention to provide a device having characteristics tending to overcome the above-indicated, as well as other, ditliculties of prior art devices.

Another object of this invention is to produce a microwave detector and/or mixer crystal unit for extremely broadband use which has good R.F. characteristics.

Still another object of the invention is to produce a microwave detector and/or mixer crystal unit which is economical and easy to fabricate.

A further object of the invention is to produce a microwave detector and/or mixer crystal unit which can be made to cover 4 and 5 to 1 frequency ranges with improved sensitivity and impedance matching characteristics.

A still further object of the invention involves the production of a microwave detector and/or mixer crystal unit which allows a simplification of the external circuitry required for broadband operation.

These and other advantages, features and objects of the invention will become more apparent from the following description taken in connection with the illustrative embodiments in the accompanying drawings, wherein:

Figure 1 illustrates a cross-section of one embodiment of my invention; and

Figure 2 represents a longitudinal section of an alternative embodiment of my invention.

Referring to Figure 1, the invention comprises a ridge waveguide having a ridge or septum 11. The ridge Waveguide may be made by any conventional method. This type of waveguide structure is designed to cover bandwidths in excess of 2 to 1 and up to 5 to I depending upon its particular application. The ridge waveguide structure inherently has a very slow ratio change of wavefguide wavelength to free'space wavel ength. .The TE mode is depressed without affecting the TE 'mode, and as a result of the dominant mode frequency bandis considerably extended.

A semi-conductor crystal 12 which may be of silicon or germanium is mounted by any conventional means, for example, by an adhesive on the wall of the ridge waveguide 10 beneath the ridge 11. A contact wire or catwhisker 13 attached to a holder 14, which also serves as an output contact, projects through the ridge into the ridge waveguide 10 so that catwhisker 13 may contact the crystal. Insulating bushings 15 and 16 support and hold holder '14 in its proper position. Were a ridge waveguide formed by pressing a blank into the top wall of a rectangular waveguide to extrude the wall, a drilled or tapped hole in said blank with insulators therein may be used. The features of the ridge waveguide enumerated above plus the reduced impedance of this structure considerably improve and simplify the external circuitry required for broadband operation.

An alternative embodiment is shown in longitudinal section in Figure 2 wherein a ridge waveguide 20 with a ridge or septum 21 therein contains a metallic crystal support 22 held in the base of the waveguide 20 by spring finger 23 attached to the waveguide by any conventional means at 24. A crystal 25 is mounted on the crystal support 22 within the waveguide and in contact with a catwhisker 26 which in turn is mounted in a holder 27. An insulating sleeve 28 supports and surrounds the catwhisker. A cap member 29 attached to the waveguide 20 by conventional means '30 holds insulating member 37 in position and supports an output unit 31. Output unit 31 comprises a sleeve 32 which contains insulating bushings 33 and 34 which grip and support holding member 35 which with pin 36 forms the output contact for the device. The mouth portion of sleeve 32 can be made of any shape suitable for receiving a mating portion which contains a contact suitable for electrically connecting with holder 27.

Thus, it can be seen that by utilizing a ridge waveguide and crystal mounted therein, the properties of broad bandwidth, good R.F. characteristics, low impedance and improved sensitivity are realized.

Although the invention has been described with reference to a particular embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.

I claim:

1. A microwave crystal detector or mixer unit for broadband operation comprising a ridge waveguide, a crystal mounted on the wall of said waveguide opposite the ridge of said waveguide, a catwhisker in contact with said crystal, an output contact connected to said catwhisker, and insulating means for supporting said output contact and catwhisker, said insulating means being located at least partially within the ridge of said ridge waveguide.

2. A microwave crystal detector or mixer unit for broadband operation comprising a ridge waveguide, a crystal holder and crystal thereon removably mounted in the wall of said waveguide opposite the ridge of said waveguide, a contact wire in contact with said crystal, an output contact, a member electrically connected to said contact wire and output contact, and insulating means within the ridge of said waveguide for supporting said member, contact wire and output contact.

3. A microwave crystal detector or mixer unit for broadband operation comprising a ridge waveguide, 21 crystal unit mounted on the wall of said waveguide opposite the ridge of said waveguide, said crystal unit having current conducting means projecting therefrom and insulating means extending through said ridge, for supporting said current conducting means, said insulating means being located'at least partially within the ridge of 5 saidridge waveguide.

2,834,884 Domenibhiniet a] May 13, 1958 

